Printed circuit boards ("PCBs") generally contain four or more layers, typically including at least one ground plane, a power plane and outer layers that provide a high density interconnect for coupling various components or sockets, which have been mounted to the PCB. Mounting components onto a PCB (or inserting them into a PCB socket) can be costly. Packaging such components (to protect them and to manage their environment) adds cost--as does adding certain devices to accommodate those components. For example, heavier components, e.g., microprocessors and their associated heat sinks, may require a retention module to secure them to the PCB. Heavy heat sinks may require use of PCB bracing elements. When components dissipate a significant amount of heat and/or cause electromagnetic interference ("EMI"), certain mechanisms may be required to address thermal and EMI issues.
Mounting packaged parts to a PCB may be undesirable for reasons other than cost. This practice exposes the components to the environment, which may increase their susceptibility to defects, and may require systems to adopt a relatively high profile. Also, mounting components to the PCB consumes PCB surface area that could otherwise be used for other purposes. In addition, for some components parasitic effects (which may result from the spacing between packaged die and associated PCB connections) may adversely affect electrical performance and signal integrity.
Accordingly, there is a need for an improved PCB that is less costly to make, when compared to those that receive certain packaged components. In particular, there is a need for such a PCB that addresses thermal, EMI, and stability requirements in a less costly fashion. There is a need for a PCB that need not allocate scarce surface area to certain packaged components, and that may facilitate relatively low profile systems. Furthermore, there is a need for a PCB that may protect the integrated circuits it contains, while reducing parasitic effects that are inherent in packaged devices. The present invention provides such a PCB.